Radamanthus
Smash Apprentice
Shyguy's Perplex Express from Mario Party 8. Of course, you'd fight on the train as it drives along. However, you'd be fighting on top of the kitchen, and the wall would be peeled away so you could see inside. The point of that is because you can jump up and down the vent/chimney things, so you can fight both on top of and inside the train. One downside to this stage would be that there probably wouldn't be any floating platforms, so it'd just be a long, flat arena on both levels.